diff --git a/insert.py b/insert.py
index 8531676..6c0c793 100755
--- a/insert.py
+++ b/insert.py
@@ -59,9 +59,9 @@ def print_clock_updated():
     if data_ts_base != 0:
         diff = data_ts - clock_ts
         if diff >= 0:
-            printf("  (data timestamp ahead by %.6fs)\n", diff)
+            printf("  (data timestamp ahead by %.6f sec)\n", diff)
         else:
-            printf("  (data timestamp behind by %.6fs)\n", diff)
+            printf("  (data timestamp behind by %.6f sec)\n", -diff)
 
 with client.stream_insert_context(args.path) as stream:
     for f in args.infile: